Multiple Sequential Oligonucleotide Primed In Situ DNA Syntheses (MULTI-PRINS)

Conventional PRINS (if it is possible to use such a description for a relatively new technique) is capable of identifying and quantifying chromosomes or chromosome pairs in metaphase or interphase cells (1 –4 ). Each PRINS reaction can only identify one pair of homologous chromosomes, because the nature of the reaction means that the product of only one primer or primer pair can be specifically labeled in each reaction. However, by inserting a blocking step after each PRINS reaction to ensure that the 3′-ends of the products of the previous reaction cannot act as primers for the next reaction, it is possible to perform several PRINS reactions on a single slide, and therefore ascertain the number of each of several pairs of chromosomes present in a given sample.